The invention described herein was made by an employee of the United States Government, and may be manufactured and used by or for the Government for governmental purposes without the payment of any royalties thereon or therefore.
The present invention relates to an apparatus and method for conditioning flow in a gas flow turbine or turbojet and for achieving power extraction to increase relative vehicle velocity. Moreover, the power which is so extracted can be recycled back into the system in order to further increase the power output and efficiency of the engine. The invention achieves the flow conditioning through use of an inlet annular flow passage which is placed upstream of the engine inlet and having one or more superconducting magnets which create a high radial magnetic field operative across the duct. Electron beams are directed in a spiral path within the magnetic field to form locally ionized regions within the annular flow path. Power can be extracted by placing an electrical load across the inlet and the outlet of the annular duct with a resulting interaction between the flowing current and the magnetic field. The power can be reintroduced into the vehicle energy system in a variety of ways, for example by the reduction of drag.
It has been known in the prior art to use various fluid dynamic means to modify flow characteristics at the inlet of a gas flow turbine. For example, U.S. Pat. No. 4,047,381 teaches the use of a flow conduit arrangement within a turbine engine which maintains in a given position with respect to the plane of the air intake, the upstream portion of reversed flow around the turbine or which even destroys the reversed flow altogether. U.S. Pat. No. 4,389,227 illustrates an air intake structure for a gas turbine engine having a mushroom shaped center portion, which along with a step downstream of the apertured wall surrounding the center portion causes liquid droplets to be launched from the center body so as to avoid introduction of the droplets into the air inlet of the engine.
It is also known to use fluid dynamic means to accomplish flow modification by means of diffusion, which typically is induced at the exit portion of the gas turbine compression stage. This process changes the gas turbine flow from low pressure, high velocity to high pressure, low velocity. However, this process does not generally contemplate inducing, let alone utilizing a change in the flow energy. Examples of this technology are represented by U.S. Pat. Nos. 5,387,081; 5,603,605; and 5,911,679.
Both of these kinds of prior art turbine technology rely on changing the architecture of the turbine structure to influence the gas flow characteristics and further both maintain substantially the same flow energy. The present invention represents a significant difference from the prior art, as it utilizes an electromagnetic means of conditioning the flow of a gas turbine or turbojet. Moreover, the invention contemplates extraction of energy from the flow to lower the flow energy into the gas turbine combustor. Lower energy in the flow enables more efficient energy addition in the combustor and can increase the flight Mach Number (xe2x80x9cNo.xe2x80x9d) of the engine.
While a highly specialized field of the prior art involves the use of electromagnetic forces imposed on gases such as xenon, and krypton for propulsion in space, these devices have no apparent application with respect gas turbine propulsion in a supersonic system, which operates at a much higher standard operating pressure. Moreover, this prior art relies on a fully ionized gas, whereas the present invention has to supply the means of ionization in the form of an electron beam gun which generates only a weakly ionized gas.
In accordance with the present invention it is novel to use an electron beam within a flow passage subjected to a magnetic field upstream of the gas turbine or turbojet inlet to influence the electromagnetics of the fluid flow, and subsequently to modify the flow at the inlet of a gas turbine. As used herein with reference to the xe2x80x9cflowxe2x80x9d, xe2x80x9cfluidxe2x80x9d and xe2x80x9cgasxe2x80x9d are used interchangeably and meant to refer to the medium or propellant, which the engine subjects to a velocity change in order to cause propulsion. In addition, the magnetic field is an annular field, and an electron beam is used in a spiral configuration. Moreover, in accordance with the present invention this modification can be used to extract power which can be reintroduced back into the propulsion system to increase the engine efficiency. This contrasts with prior art techniques of flow modification which did not intentionally modify the turbine flow energy and the turbine power, and which relied solely on structural modification to the flow housing to influence the flow dynamics.
In addition, the present invention can use the extracted energy to boost the overall power of the drive system, for example, by using the energy for drag reduction. However, the invention could be used for other, or broader applications. This redirection of energy or energy by-pass can be used for example, to influence or xe2x80x9csoftenxe2x80x9d the shock waves at the bow of the jet vehicle. Theoretically, the drag to which the vehicle is subjected can be changed by altering the profile of the shock wave at the bow of the vehicle. The consequence is more apparent power to the vehicle, and the ability to achieve higher Mach speeds. The invention can also be used to influence the thermodynamic characteristics of the drive system. If kinetic energy is extracted from the gas turbine or turbojet inlet, then this energy is not available for conversion to thermal energy by a diffusion process thus reducing the temperature that the gas enters the gas combustor and further enabling the addition of more energy into the turbine combustion process before reaching the temperature limitations of the turbine material. The redirected energy can be reintroduced at the turbine outlet in the form of velocity. Thus, the use of magneto hydrodynamic (xe2x80x9cMHDxe2x80x9d) flow conditioning at high speeds permits the addition of energy in the gas turbine combustor without increasing the operating temperature of the engine so as to exceed the physical limitations of the engine structure. Magneto hydrodynamic flow is also referred to as magneto-gasdynamic flow.
One of the objects of the present invention is to lower the gas energy at the engine inlet in order to increase the temperature differential available for energy addition in the gas turbine combustor. This is accomplished by using MHD power extraction to shift the location at which the velocity component of the inlet flow energy is introduced into the system, i.e. from the inlet of the gas turbine to the outlet of the gas turbine and/or this energy could be used to accomplish drag reduction on the vehicle, by softening the shock wave on the vehicle. Other uses of the energy to increase the efficiency of the operating system such as the auxiliary power and magnetohydrodynamic flow acceleration are contemplated as being within the scope of this invention.
A further object of the invention is to use electron beams to influence the fluid flow in a gas turbine by bombarding the atoms and stripping off electrons to generate a partially ionized fluid comprising free ions and charged particles. This enables the charged particles to interact with the electro-magnetic field.
The invention comprises an inlet annular flow passage without mechanical obstruction or a xe2x80x9cductxe2x80x9d member which is placed upstream of, preferably contiguous to, the inlet of a gas turbine engine. As used herein xe2x80x9cgas flow turbine enginexe2x80x9d contemplates the use of the invention within a gas turbine engine such as used for an airline, or a turbojet as is used for a high-speed aircraft, and similar high-speed flow applications. A superconducting electromagnet is placed around the annular duct such that a high magnetic field, which is preferably radial, is operative across the duct. Around the duct on both the inside and outside walls, small slots are cut in the walls, directly opposite one another, like the threads of a screw. Electron beams are passed through these slots. These electron beams collide with molecules in the inlet duct flow and locally ionize them in an efficient manner. Once ionized, the molecules interact with the magnetic field and act to retard the flow. Power is extracted from this interaction, by placing an electrical load across the inlet and exit of the annular duct. The electrical current flow through the annular duct is along the spiral path of ions in the flow formed by the electron beams. This flow interaction will cause a swirl in the inlet flow, which can be easily accommodated by inlet guide vanes on the gas turbine. While the foregoing represents the preferred embodiment for implementation of the electromagnetic field and power extraction, the invention also encompasses differing configurations, which would include rectilinear inlet geometries with unidirectional B-fields. Additionally, while opposing spiraling electron guns have been described, the path of the guns may have a different shape, or even a single gun may be used.